Electrically conductive bonding material is a general term for the electrically conductive adhesive agent and an electrically conductive joining agent. In the other words, the electrically conductive adhesive agent indicates an agent that is used for allowing the metals to adhere to each other at lower temperature than a melting point of electrically conductive metallic powder. The electrically conductive joining agent indicates an agent that is used for melting the electrically conductive metallic powder and joining metals to each other.
Solder has been often used as the electrically conductive joining agent for joining various kinds of electronic circuits to a circuit board and the solder has been melted so that various kinds of electronic circuits are joined to the circuit board. Although lead-free solder such as Sn—Ag—Cu or the like has been used as solder material, taking into consideration any environmental influences, this solder has a higher liquidus temperature than that of the conventional lead-containing solder by 30 degrees C. or higher. Since temperature within a reflow furnace is very higher than the liquidus temperature, this gives a high thermal shock (thermal stress) to the electronic parts and/or the circuit board to be joined.
Parts-joining material using the electrically conductive adhesive agent has been studied with the object of reducing the thermal stress. This electrically conductive adhesive agent contains electrically conductive metallic powder, thermosetting resin, a hardening agent and a hardening accelerator and pieces of the electrically conductive metallic powder are densely contacted to each other following the hardening of the resin by heating so that various kinds of electronic circuits can be joined to the circuit board without melting the electrically conductive metallic powder (see patent documents 1 and 2).